Method and casting core for forming a landing for welding a baffle inserted in  an airfoil

ABSTRACT

A method and casting core for forming a landing for welding a baffle inserted into an airfoil are disclosed, wherein the baffle landing of the blade or vane is formed in investment casting by the casting core rather than by wax, reducing tolerances and variability in the location of the baffle inserted into the cooling cavity of airfoil when the baffle is welded to the baffle landing.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. Ser. No. 12/981,630, filedDec. 30, 2010, the contents of which are incorporated by referenceherein in their entirety.

STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The invention was made with U.S. Government support under contract No.N00019-02-C-3003 awarded by the U.S. Navy. The U.S. Government may havecertain rights in the invention.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates generally to baffles forimpingement cooling of airfoils for gas turbine engines and, moreparticularly, to a method and casting core for forming a landing forwelding a baffle inserted in an airfoil.

Gas turbine engines, such as those used to power modem commercialaircraft, to power sea vessels, to generate electrical power, and inindustrial applications, include a compressor for pressurizing a supplyof air, a combustor for burning a hydrocarbon fuel in the presence ofthe pressurized air, and a turbine for extracting energy from theresultant combustion gases. Generally, the compressor, combustor andturbine are disposed about a central engine axis with the compressordisposed axially upstream of the combustor and the turbine disposedaxially downstream of the combustor. In operation of a gas turbineengine, fuel is injected into and combusted in the combustor incompressed air from the compressor thereby generating high-temperaturecombustion exhaust gases, which pass through the turbine in order toproduce rotational shaft power. The shaft power is used to turn aturbine for driving a compressor to provide air to the combustionprocess to generate the high energy gases. Additionally, the shaft poweris used to power a secondary turbine to, for example, drive a generatorfor producing electricity, or to produce high momentum gases forproducing thrust.

The turbine includes a plurality of turbine stages, wherein each stageincludes a stator section formed by a row of stationary vanes followedby a rotor section formed by a row of rotating blades. In each turbinestage, the upstream row of stationary vanes directs the combustionexhaust gases against the downstream row of blades. In order to producegases having sufficient energy to drive both the compressor and thesecondary turbine, it is necessary to compress the air to elevatedtemperatures and to combust the air, which again increases thetemperature. Thus, the vanes and blades, each having an airfoil, aresubjected to extremely high temperatures of the combustion exhaustgases, often times exceeding the melting point of the alloys used tomake the airfoils.

The airfoils are maintained at temperatures below their melting pointby, among other things, cooling the airfoils with a supply of relativelycooler air that is typically siphoned from the compressor. The coolingair is directed into the blade or vane to provide cooling of the airfoilthrough various modes, including impingement cooling. Specifically, thecooling air is passed into an interior of the airfoil through one ormore cooling cavities in the airfoil to remove heat from the alloy. Insome implementations, the cooling air is directed into one or morebaffles installed within the cooling cavities in the airfoil and havinga plurality of cooling holes. Cooling air flowing through the coolingholes of the baffle impinges on and flows against an interior surface ofthe airfoil. The cooling air then moves through film cooling holes inthe airfoil to pass over the outer surface of the airfoil to prevent thehot gases from contacting the vane or blade.

As a general matter, the cooling air effectiveness of the baffle incooling the airfoil is dependent upon the size of the impingementdistance between the side portion of the baffle and the airfoil.Typically, there is an optimum distance between the baffle and theairfoil where cooling effectiveness is maximized. If the distancebetween the baffle and the airfoil is greater than the optimum distance,the cooling air disperses too much and the cooling effectivenessdecreases. On the other hand, when the distance between the baffle andthe airfoil is less than the optimum distance, the cooling air does notturbulate or expand sufficiently and the cooling effectivenessdecreases. Also, when there are two baffles disposed in the same coolingcavity (i.e., one welded to the outer platform and one welded to theinner platform), the cooling air effectiveness of the baffles isaffected by the distance (or gap) between the bottom of the two bafflesinside the cooling cavity of the airfoil, with a smaller gap providing agreater amount of impingement cooling than a larger gap.

Baffles are hollow, sheet metal sock structures manufactured separatelyfrom the airfoil and later welded to landings on the platforms of theblades or vanes provided for that purpose. The blades or vanes,including the platforms and the airfoil, are typically manufacturedusing investment casting, a known technique for forming metalliccomponents having complex geometries, especially hollow gas turbineengine components. During the investment casting process, the surfacesof platforms of the blades or vanes, including the baffle landings, areinitially formed by wax, which can result in relatively high tolerancesfor the distance between the platforms that, in turn, determines thelength of the airfoil cooling cavity into which the baffles areinserted. In addition, the surface profiles of the baffle landingsinitially formed on the platforms by wax are undulated, also resultingin relatively high surface tolerances. The relatively high tolerancesfor these landings can create problems when inserting the baffles intothe cooling cavities of the airfoil.

For example, these relatively high tolerances can create relativelysignificant variability in the gap left between the baffle and theairfoil when the baffle is welded to the platform baffle landings. Thisis of particular concern where the cooling cavity is conic with largefillets and the baffle follows the conic shape of the cooling cavity.These relatively high tolerances can also create relatively significantvariability in the gap left between two baffles when welded to thebaffle landings at opposite ends of the cooling cavity. These gapsbetween the baffles and the airfoil and between the baffles themselvesaffect the cooling air effectiveness of the baffles as discussedpreviously. Similarly, if the distance between the inner platform andouter platform is too small as a result of the cumulative tolerances,there may not be sufficient length in the cooling cavity to insert twobaffles as they would clash in the cooling cavity rather than leaving agap. There is, therefore, a need to provide less variability in thelocation of the baffles inserted into the cooling cavities of airfoilswhen the baffles are welded to the baffle landings of the blades orvanes.

BRIEF SUMMARY OF THE INVENTION

A method and casting core for forming a landing for welding a baffleinserted into an airfoil are disclosed, wherein the baffle landing ofthe blade or vane is formed in investment casting by the casting corerather than by wax, reducing tolerances and variability in the locationof the baffle inserted into the cooling cavity of airfoil when thebaffle is welded to the baffle landing.

According to one embodiment, a method of forming a landing for welding abaffle inserted into a cooling cavity of an airfoil is provided. Themethod comprises the steps of forming a casting core having a firstportion in the shape of the landing, overmolding the casting core withwax to form a casting pattern having a first portion in the shape of thelanding, shelling the casting pattern with a shell, removing the castingpattern to form a void between the shell and the casting core, pouringmetal into the void to surround the casting core, and removing theshell, wherein the landing is formed by the first portion of the castingcore in the shape of the landing.

In another embodiment, a method of forming a first landing for welding afirst baffle inserted into a cooling cavity of an airfoil and a secondlanding for welding a second baffle inserted into the cooling cavity isprovided. The method comprises the steps of forming a casting corehaving a first portion in the shape of the first landing and a secondportion in the shape of the second landing, overmolding the casting corewith wax to form a casting pattern having a first portion in the shapeof the first landing and a second portion in the shape of the secondlanding, shelling the casting pattern with a shell, removing the castingpattern to form a void between the shell and the casting core, pouringmetal into the void to surround the casting core, and removing theshell, wherein the first landing is formed by the first portion of thecasting core in the shape of the first landing and the second landing isformed by the second portion of the casting core in the shape of thesecond landing.

In yet another embodiment, a casting core for forming a first landingfor welding a first baffle inserted into a cooling cavity of an airfoilis provided, wherein a first portion of the casting core is the shape ofthe first landing.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the disclosure, reference will be made tothe following detailed description which is to be read in connectionwith the accompanying drawing, wherein:

FIG. 1 is a perspective view of an exemplary stationary turbine vanehaving an airfoil with a plurality of cooling cavities.

FIG. 2 is a cross-sectional view of the exemplary stationary turbinevane of FIG. 1.

FIG. 3 is a flowchart of an exemplary method for investment casting theexemplary stationary turbine vane of FIG. 1.

FIG. 4 illustrates a prior art method and casting core for formingbaffle landings for welding baffles in an airfoil.

FIG. 5 illustrates a method and casting core for forming baffle landingsfor welding baffles in an airfoil.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view of an exemplary stationary turbine vane 10having an airfoil 20 with a plurality of cooling cavities 30, 32spanning the length of the airfoil 20. Although the embodiment isdisclosed using an exemplary stationary turbine vane, the inventiveconcepts disclosed herein are not limited to stationary turbine vanes,but can be applied to other turbine blades and vanes having airfoils 20with one or more cooling cavities 30, 32 for inserting a first baffle 40(e.g., a vane used in the compressor section of a gas turbine engine).

Returning to FIG. 1, the stationary turbine vane 10 receives hightemperature gas G and cooling air A in a turbine section of a gasturbine engine. Turbine vanes 10 operate to increase the efficiency ofthe gas turbine engine in which they are installed. The turbine vane 10has an outer platform 12, an inner platform 14, and airfoil 20. Theouter platform 12 and the inner platform 14 are connected to adjacentplatforms within the gas turbine engine to form structures between whicha plurality of airfoils 20 are supported. The outer platform 12 andinner platform 14 increase the efficiency of the gas turbine engine byforming outer and inner boundaries for the flow of high temperature gasG through the gas turbine engine, preventing the escape of hightemperature gas G from the gas turbine engine such that more air isavailable for performing work. The shape of vane 10 also increases theefficiency of the gas turbine engine. Vane 10 generally functions toredirect the trajectory of high temperature gas G coming from acombustor section or a blade of an upstream turbine stage to a blade ofa downstream turbine stage.

The outer diameter end of the airfoil 20 mates with the outer platform12, and the inner diameter end of the airfoil 20 mates with the innerplatform 14. The airfoil 20 has a leading edge 22, a trailing edge 24, apressure side 26, and a suction side 28. High temperature gas G flowsacross vane the 10, impinges on leading edge 22 of the airfoil 20 andflows across the pressure side 26 and he suction side 28 of the airfoil20. The pressure side 26 and the suction side 28 of the airfoil 20redirect the flow of high temperature gas G received at the leading edge22 such that, after passing by the trailing edge 24, the incidence ofhigh temperature gas G on the subsequent rotor blade stage is optimized.As such, more work can be extracted from the interaction of hightemperature gas G with downstream blades.

The efficiency of the gas turbine engine is also improved by increasingthe temperature to which the vane 10 can be subjected. For example, thevane 10 is often positioned immediately downstream of a combustorsection of a gas turbine engine where the temperature of hightemperature gas G is hottest. The airfoil 20 is, therefore, subjected toa concentrated, steady stream of high temperature gas G during operationof the gas turbine engine. The extremely elevated temperatures ofcombustion high temperature gas G often exceed the melting point of thematerial forming the vane 10. The airfoil 20 is therefore cooled usingcooling air A provided by, for example, relatively cooler air bled froma compressor section within the gas turbine engine and forced through aplurality of cooling cavities 30, 32 in the airfoil 20, including aleading edge cooling cavity 30 and a trailing edge cavity 32. Both theinner platform 12 and the outer platform 14 have a non-gas path side 16,where the cooling air A flows, and a gas-path side 18 where the hightemperature gas G flows.

In this exemplary embodiment shown in FIG. 1, a first baffle 40 with aplurality of cooling holes 42 is inserted through the outer platform 12in the leading edge cooling cavity 30. Cooling air A enters the firstbaffle 40, passes through cooling holes 42 and enters the cooling cavity30 to perform impingement cooling on the interior of the airfoil 20. Thefirst baffle 40 is typically joined, such as by welding, to the outerplatform 12. In the exemplary embodiment, a second baffle 50 (notvisible in FIG. 1) is inserted through the inner platform 14 in theleading edge cooling cavity and is typically joined, such as by welding,to the inner platform 14.

FIG. 2 is a cross-sectional view of the exemplary stationary turbinevane 10 of FIG. 1. As shown in the figure, there is a distance Z betweenthe outer platform 12 and the inner platform 14. FIG. 2 also shows thefirst baffle 40 welded to first baffle landings 13 on the outer platform12 and the second baffle 50 welded to second baffle landings 15 on theinner platform 14. The baffles 40, 50 are inserted into the coolingcavity 30 of the airfoil 20 in a configuration that provides a distanceX between the bottom portions of the two baffles 40, 50 and a distance Ybetween the side portions of the two baffles 40, 50 and the conicinterior surface of the airfoil 20, which has large fillets. Thedistance Y is the impingement cooling distance. Although the embodimentdisclosed includes a plurality of baffles 40, 50, it will be understoodthat a single baffle may also be used.

As can be seen in FIG. 2, if the distance Z between the outer platform12 and the inner platform 14 were to vary based on manufacturingtolerances allowing the platforms 12, 14 to shift relative to eachother, the distance X between the bottom portions of the two baffles 40,50 and the distance Y between the side portions of the two baffles 40,50 and the conic interior surface of the airfoil 20 would also vary. Forexample, if the distance Z were to decrease from what is shown in FIG.2, causing the first baffle landings 13 to be closer to the secondbaffle landings 15, the distance X would also decrease. In a case wherethe distance Z decreased significantly, the distance X could becompletely eliminated, preventing the first baffle 40 from beinginstalled in the same cooling cavity 30 as the second baffle 50 as theywould clash during installation. On the other hand, if the distance Zwere to increase from what is shown in FIG. 2, causing the first bafflelandings 13 to be further from the second baffle landings 15, thedistance X would also increase, decreasing the amount of impingementcooling provided by the baffles 40, 50. In addition, variability in thedistance Z would cause the distance Y between the side portions of thebaffles 40, 50, and the interior of the airfoil 20, all of which areconic, to vary from an optimum distance, decreasing the amount ofimpingement cooling effectiveness provided by the baffles 40, 50. Thedistances X, Y are also affected by variability in the location of thebaffle landings 13, 15 apart from the distance Z. For example, if thesurface profiles of both the first baffle landings 13 and the secondbaffle landings 15 were to be raised or lowered, this would also movethe baffles 40, 50 with respect to each other and the interior surfaceof the airfoil. As discussed previously, the turbine vane 10, includingthe airfoil 20, the platforms 12, 14, the baffle landings 13, 15 aretypically manufactured using investment casting. By manufacturing thebaffle landings 13, 15 in a manner that minimizes tolerances, which, inturn, greatly reduces the variability in the location of the bafflelandings 13, 15, many of these issues can be resolved.

FIG. 3 is a flowchart of an exemplary method 100 for investment castingthe exemplary stationary turbine vane of FIG. 1. Other methods arepossible, including a variety of prior art methods and yet-developedmethods. Initially, a moderately flexible ceramic polymer casting corein the shape of a cooling cavity 30 is molded 102 by injection molding.For ease of discussion, the investment casting process is described withrespect to only one of the cooling cavities 30, 32, the leading edgecavity 30. After forming the ceramic polymer casting core and letting itcool 110, the casting core is placed into a furnace where it is heated120 to burn out and remove the polymer, leaving a rigid ceramic castingcore. Other casting cores can also be used, including casting coresformed with refractory metal (RMCs).

The casting core is placed in a die and then overmolded 130 with aneasily sacrificed material such as a natural or synthetic wax. Theovermolded casting core forms a casting pattern with an exterior shapelargely corresponding to the exterior shape of the airfoil 20 andplatforms 12, 14. The casting pattern may then be assembled 132 to ashelling fixture (e.g., via wax welding between end plates of thefixture). The casting pattern may then be shelled 134 (e.g., via one ormore stages of slurry dipping, slurry spraying, or the like). After theshell is built up, it may be dried 136. The drying provides the shellwith at least sufficient strength or other physical integrity propertiesto permit subsequent processing. For example, the shell containing theinvested casting core may be disassembled 138 fully or partially fromthe shelling fixture and then transferred 140 to a dewaxer (e.g., asteam autoclave). In the dewaxer, a steam dewax process 142 removes amajor portion of the wax leaving the casting core secured within theshell. The shell and casting core will largely form the ultimate mold.However, the dewax process typically leaves a wax or byproducthydrocarbon residue on the shell interior and the casting core.

After the dewax, the shell is transferred 144 to a furnace (e.g.,containing air or other oxidizing atmosphere) in which it is heated 146to strengthen the shell and remove any remaining wax residue (e.g., byvaporization) and/or converting hydrocarbon residue to carbon. Oxygen inthe atmosphere reacts with the carbon to form carbon dioxide. Removal ofthe carbon is advantageous to reduce or eliminate the formation ofdetrimental carbides in the metal casting. Removing carbon offers theadditional advantage of reducing the potential for clogging the vacuumpumps used in subsequent stages of operation.

The mold may be removed from the atmospheric furnace, allowed to cool,and inspected 148. The mold may be seeded 150 by placing a metallic seedin the mold to establish the ultimate crystal structure of adirectionally solidified (DS) casting or a single-crystal (SX) casting.The present teachings may be applied to other DS and SX castingtechniques (e.g., wherein the shell geometry defines a grain selector)or to casting of other microstructures. The mold may be transferred 152to a casting furnace (e.g., placed atop a chill plate in the furnace).The casting furnace may be pumped down to vacuum 154 or charged with anon-oxidizing atmosphere (e.g., inert gas) to prevent oxidation of thecasting alloy. The casting furnace is heated 156 to preheat the mold.This preheating serves two purposes: to further harden and strengthenthe shell, and to preheat the shell for the introduction of molten alloyto prevent thermal shock and premature solidification of the alloy.

After preheating and while still under vacuum conditions, the moltenalloy is poured 158 into the mold and the mold is allowed to cool tosolidify 160 the alloy (e.g., after withdrawal from the furnace hotzone). After solidification, the vacuum may be broken 162 and thechilled mold removed 164 from the casting furnace. The shell may beremoved in a deshelling process 166 (e.g., mechanical breaking of theshell).

The casting core is removed in a decoring process 168 to leave a castarticle (e.g., a metallic precursor of the ultimate part). The castarticle may be machined 170, chemically and/or thermally treated 172 andcoated 174 to form the ultimate part. Some or all of any machining orchemical or thermal treatment may be performed before the decoring.

FIG. 4 illustrates a prior art method and casting core 210 for formingbaffle landings 13, 15 for welding baffles 40, 50 in an airfoil 20 usingthe exemplary method 100 of FIG. 3. As can be seen in the figure, acasting core 210 is formed in the shape of a cooling cavity 30 andplaced in a die (not shown) in the shape of the airfoil 20 and platforms12, 14, including the baffle landings 13, 15. Wax 220 is injectionmolded into the die where it fills in the voids between the casting core210 and the die and overmolds the casting core 210 forming a castingpattern in the shape of the exterior of the airfoil 20 and the platforms12, 14, including the baffle landings 13, 15. Notably, it is the wax 220that initially forms the shape of the platforms 12, 14, including thebaffle landings 13, 15, as the casting core 210 only forms the shape ofthe cooling cavity 30 of the airfoil 20 as the diameter of the castingcore 210 extending beyond the platforms 12, 14 does not exceed thediameter of the cooling cavity 30 where the airfoil 20 mates with theplatforms 12, 14. This wax 220 is then shelled by covering the castingpattern with a ceramic slurry shell 230. After the ceramic slurry shell230 dried and hardened, the wax 220 casting pattern is removed leaving avoid between the ceramic slurry shell 230 and the casting core 210 inthe shape of the airfoil 20 and the platforms 12, 14. This void wherethe wax 220 once resided is later filled by a molten alloy 240 thatengulfs the casting core 210 in metal and ultimately forms the airfoil20 and the platforms 12, 14. The ceramic slurry shell 230 is knocked offand the casting core 210 is removed (e.g., by using a caustic liquid)leaving the finished part behind.

With reference again to FIG. 2, it has been found that using the priorart method and casting core 210 as illustrated in FIG. 4, the distance Zbetween the outer platform 12 initially formed by the wax 220 and theinner platform 14 initially formed by the wax 220 can have a toleranceas high as ±0.014 in. (0.3556 mm). It has also been found that thesurface profiles of both the first baffle landings 13 initially formedby the wax 220 and the second baffle landings 15 initially formed by thewax 220 can have tolerances as high as ±0.015 in. (0.381 mm) for eachlanding 13, 15, resulting in a cumulative tolerance of up to ±0.044 in.(1.1176 mm)) for wax 220 tolerances alone. In addition, it has beenfound that the cooling cavity 30 formed by the casting core 210 canshift relative to the platforms 12, 14 by as much as 0.015 in. (0.381mm) in one direction and by as much as 0.030 in. (0.762 mm) in the otherdirection. These relatively high tolerances can cause the distance Xbetween the bottom portions of the two baffles 40, 50 and the distance Ybetween the side portions of the two baffles 40, 50 and the conicinterior surface of the airfoil 20 to vary greatly as describedpreviously. It has also been found the tolerances for parts formed bythe casting core 210 (e.g., the cooling cavity 30 of the airfoil 20formed by the ceramic casting core) have much lower tolerances (e.g.,±0.004 in (0.1016 mm))

FIG. 5 illustrates a method and casting core 310 for forming bafflelandings 13, 15 for welding baffles 40, 50 in an airfoil 20 using theexemplary method 100 of FIG. 3. As can be seen in the figure, at least afirst portion 312 of the casting core 310 is formed in the shape of thefirst baffle landings 13, a second portion 314 of the casting core isformed in the shape of the second baffle landings 15, and a thirdportion 316 of the casting core 310 is formed in the shape of thecooling cavity 30, and placed in a die (not shown) in the shape of theairfoil 20 and platforms 12, 14, including the baffle landings 13, 15.Wax 320 is injection molded into the die where it fills in the voidsbetween the casting core 310 and the die and overmolds the casting core310 forming a casting pattern in the shape of the exterior of theairfoil 20 and the platforms 12, 14, including the baffle landings 13,15. Notably, the wax 320 initially forms the shape of the platforms 12,14, except for the baffle landings 13, 15, as the casting core 310 formsthe shape of the cooling cavity 30 of the airfoil 20 and the bafflelandings 13, 15 as the diameter of the first portion 312 and secondportion 314 of the casting core 310 extending beyond the platforms 12,14 exceeds the diameter of the cooling cavity 30 where the airfoil 20mates with the platforms 12, 14 to form the baffle landings 13, 15. Thiswax 320 is then shelled by covering the casting pattern with a ceramicslurry shell 330. After the ceramic slurry shell 330 is dried andhardened, the wax 320 casting pattern is removed leaving avoid betweenthe ceramic slurry shell 330 and the casting core 310 in the shape ofthe airfoil 20 and the platforms 12, 14. This void where the wax 320once resided is later filled by a molten alloy 340 that engulfs thecasting core 310 in metal and ultimately forms the airfoil 20 and theplatforms 12, 14. The ceramic slurry shell 330 is knocked off and thecasting core 310 is removed (e.g., by using a caustic liquid) leavingthe finished part behind.

With reference again to FIG. 2, it has been found that using the methodand casting core 310 as illustrated in FIG. 5, the distance Z betweenthe portions of the outer platform 12 initially formed by the wax 320and portions of the inner platform 14 initially formed by the wax 320does not have any effect on the relative location of the baffle landings13, 15, which are now fixed by the casting core 310 that includes theshape of the baffle landings 13, 15. It has also been found that thesurface profiles of both the first baffle landings 13 initially formedby the casting core 310 and the second baffle landings 15 initiallyformed by the casting core 310 can have tolerances of only ±0.004 in(0.1016 mm) for each landing 13, 15, resulting in a cumulative toleranceof only ±0.008 in (0.2032 mm)). It has also been found that the use ofthe casting core 310 to form the baffle landings 13, 15 eliminates anytolerances associated with the shifting of the cooling cavity 30 formedby the casting core 310 relative to the platforms 12, 14. Theserelatively low or eliminated tolerances minimize the variability of thedistance X between the bottom portions of the two baffles 40, 50 and thedistance Y between the side portions of the two baffles 40, 50 and theconic interior surface of the airfoil 20, improving the coolingeffectiveness of the baffles 40, 50 and simplifying installation of thebaffles 40, 50.

The terminology used herein is for the purpose of description, notlimitation. Specific structural and functional details disclosed hereinare not to be interpreted as limiting, but merely as basis for teachingone skilled in the art to employ the present invention. While thepresent invention has been particularly shown and described withreference to the exemplary embodiments as illustrated in the drawing, itwill be recognized by those skilled in the art that variousmodifications may be made without departing from the spirit and scope ofthe invention. Those skilled in the art will also recognize theequivalents that may be substituted for elements described withreference to the exemplary embodiments disclosed herein withoutdeparting from the scope of the present invention.

Therefore, it is intended that the present disclosure not be limited tothe particular embodiment(s) disclosed as, but that the disclosure willinclude all embodiments falling within the scope of the appended claims.

What is claimed is:
 1. A method of forming a first landing for welding a first baffle inserted into a cooling cavity of an airfoil comprising the steps of: forming a casting core having a first portion in the shape of the first landing; overmolding the casting core with wax to form a casting pattern having a first portion in the shape of the first landing; shelling the casting pattern with a shell; removing the casting pattern to form a void between the shell and the casting core; pouring metal into the void to surround the casting core; and removing the shell, wherein the first landing is formed by the first portion of the casting core in the shape of the first landing.
 2. The method of claim 1, wherein the step of forming a casting core having a first portion in the shape of the first landing is performed by injection molding.
 3. The method of claim 1, wherein the casting core is a ceramic polymer.
 4. The method of claim 1, wherein the casting core is a refractory metal core.
 5. The method of claim 1, wherein the step of shelling the casting pattern with a shell is performed using a ceramic slurry.
 6. The method of claim 1, wherein the tolerance of the surface profile of the first landing is not greater than 0.004 in. (0.1016 mm).
 7. The method of claim 1, further comprising the steps of: forming a casting core having a second portion in the shape of a second landing for welding a second baffle inserted into the cooling cavity of the airfoil; and overmolding the casting core with wax to form a casting pattern at least a portion of which is in the shape of the second landing, wherein the second landing is formed by the second portion of the casting core in the shape of the second landing.
 8. A method of forming a first landing for welding a first baffle inserted into a cooling cavity of an airfoil and a second landing for welding a second baffle inserted into the cooling cavity comprising the steps of: forming a casting core having a first portion in the shape of the first landing and a second portion in the shape of the second landing; overmolding the casting core with wax to form a casting pattern having a first portion in the shape of the first landing and a second portion in the shape of the second landing; shelling the casting pattern with a shell; removing the casting pattern to form a void between the shell and the casting core; pouring metal into the void to surround the casting core; and removing the shell, wherein the first landing is formed by the first portion of the casting core in the shape of the first landing and the second landing is formed by the second portion of the casting core in the shape of the second landing.
 9. The method of claim 8, wherein the step of forming a casting core having a first portion in the shape of the first landing and a second portion in the shape of the second landing is performed by injection molding.
 10. The method of claim 8, wherein the casting core is a ceramic polymer.
 11. The method of claim 8, wherein the casting core is a refractory metal core.
 12. The method of claim 8, wherein the step of shelling the casting pattern with a shell is performed using a ceramic slurry.
 13. The method of claim 8, wherein the tolerance of the surface profile of the first landing and second landing is not greater than 0.004 in. (0.1016 mm).
 14. A casting core for forming a first landing for welding a first baffle inserted into a cooling cavity of an airfoil comprising: a first portion in the shape of the first landing.
 15. The casting core of claim 14, further comprising a second portion in the shape of a second landing for welding a second baffle inserted into the cooling cavity.
 16. The casting core of claim 14, wherein the casting core is a ceramic polymer.
 17. The casting core of claim 14, wherein the casting core is a refractory metal core.
 18. The casting core of claim 14, further comprising a third portion in the shape of the cooling cavity. 